Method and apparatus for allocating sounding resources in a wireless network

ABSTRACT

A computing apparatus for allocating sounding resources in an access node of a wireless network. The computing apparatus comprises a processor configured to determine a first device state based on a device state model and first device information, wherein the first device state model includes a finite number of states. The processor is configured to determine a first target sounding configuration for the first device information based on the first device state, and output the first target sounding configuration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No.PCT/EP2015/062581, filed on Jun. 5, 2015, the disclosure of which ishereby incorporated by reference in its entirety.

TECHNICAL FIELD

The aspects of the present disclosure relate generally to wirelesscommunication systems and in particular to allocation of soundingreference symbol resources.

BACKGROUND

The increase in the number of mobile devices subscribing to Long TermEvolution (LTE) type wireless communication systems has created highcell loads, both in terms of resource block (RB) utilization(e.g., >75%) and the number of simultaneously connected or on-linedevices in a cell. Mobile users are expected to enjoy a wide-range ofmobile applications generating diverse types of “smart phone traffic”,with a spread of data packet sizes and inter-packet arrival times. Theseconditions are favorable for achieving large gains through the use ofmulti-user diversity and frequency selective scheduling (FSS), therebyproviding an improved smart phone experience to their users.

When the number of mobile devices in a cell is large, it is notpractical to give rich channel state information (CSI) signaling toevery on-line mobile device to achieve good FSS. Rich CSI signalingmeans detailed sub-band CSI across the entire carrier bandwidth with arelatively short update period. This can result in large signalingoverhead, and may exhaust all available sounding reference symbol (SRS)resources due to repeated transmission of SRS on each sub-band by allon-line mobile devices. High cell loads make it difficult to manage SRStransmission and allocate sounding resources to mobile devices in a waythat maximizes important performance metrics such as cell uplinkthroughput or uplink throughput of mobile devices located near the edgeof a cell. Rich CSI is essential for accurate FSS. Knowledge of thefrequency response across the whole bandwidth allows identification ofthe best frequency bands for each mobile device.

Frequency specific CSI should remain accurate across multiple schedulingperiods, such as 1 millisecond in LTE, before it is refreshed withanother sounding. Frequent CSI measurement is necessary even for slowmoving mobile devices. For example, sounding the whole band every 20 ms(with individual sub-band sounding transmissions every 5 ms) isrecommended for pedestrian users moving at about 3 km/h. For highermobile user speeds, the reporting interval should drop in inverseproportion to the speed. Rich sounding comes at a cost. For example, insome conventional networks every sub-frame may be configured to use oneSC-FDMA symbol as a SRS, resulting in a sounding overhead of 1/12th orabout 8%. It is therefore desirable to configure a mobile device forrich sounding only when necessary. The sounding configuration, or SRSreporting configuration, of a mobile device may be changed through theuse of a radio resource control (RRC) connection reconfigurationprocedure. While, the resource block cost of a RRC connectionreconfiguration is low, it does consume a number of physical downlinkcontrol channel (PDCCH) resources. There is also a risk of encounteringa radio link failure and dropping a call when a mobile device isencountering poor radio conditions such as when the mobile device is atthe edge of a cell. Because of this, it is recommended to keep the RRCconnection reconfigurations low, such as less than one hertz per mobiledevice.

Thus, there is a need for methods and apparatus for assigning soundingresources to mobile devices that effectively maximize desiredperformance criteria, such as throughput of cell edge users, while atthe same time keeping RRC connection reconfigurations to a minimum.

SUMMARY

It is an object of the present disclosure to provide apparatus andmethods that can allocate sounding resources in a radio access networksuch that mobile devices likely to achieve the greatest throughputimprovements receive the richest sounding configurations withoutexcessive radio resource control reconfigurations.

According to a first aspect of the present disclosure the above andfurther objects and advantages are obtained by a computing apparatus foruse in an access node. The computing apparatus includes a processorconfigured to determine a first device state based on a device statemodel and first device information, wherein the device state modelcomprises a finite number of states. The processor then determines afirst target sounding configuration for the first device informationbased on the first device state and outputs the first target soundingconfiguration. In this manner, richer sounding configurations areprovided without excessive radio resource control reconfigurations.

In a first possible implementation form of the computing apparatusaccording to the first aspect the processor is configured to determinethe first device state based on an amount of data in a transmit buffer.This allows for richer sounding configurations to be provided to mobiledevices requiring transmission of larger amounts of data.

In a second possible implementation form of the computing apparatusaccording to the first aspect as such or to the first possibleimplementation form of the first aspect the processor is configured tomove the first device state to a higher buffer state when the amount ofdata in the transmit buffer exceeds a first predetermined threshold fora first predetermined period of time, and to move the first device stateto a lower buffer state when the amount of data in the transmit bufferdrops below a second predetermined threshold for a second predeterminedperiod of time. In this manner, reliable device state determination isachieved.

In a third implementation form of the computing apparatus according tothe first aspect the processor is configured to determine the firstdevice state based on an amount of data in the transmit buffer, anamount of data transmitted, and a traffic type. In this manner, improveddetermination of a device state is achieved.

In a fourth implementation form of the computing apparatus according tothe first aspect the processor is configured to determine the firstdevice state based on a current and past quantity of resource blocks inthe first device information and/or a current and past frequency of datatransmissions in the first device information. This enables improvedallocation of sounding resources.

In a fifth implementation form of the computing apparatus according tothe first aspect as such or to the fourth implementation form of thefirst aspect the processor is configured to estimate a deviceinformation value for a next time period based on one or more pastdevice information values, and determine the resource block state basedon the estimated device information value. This allows for improvedallocation of sounding resources to be achieved.

In a sixth possible implementation form of the apparatus according tothe first aspect as such or to any of the preceding first through fifthimplementation forms of the first aspect the processor is configured todetermine a second device state based on the device state model and asecond device information, determine a second target soundingconfiguration, wherein the second target sounding configurationcomprises fewer sounding resources than a current sounding configurationof the second device information, and when available sounding resourcesfor a cell are insufficient to support the first target soundingconfiguration, output the second target sounding configuration toincrease the available sounding resources in the cell. This provides forswapping of sounding resources between mobile devices requiringadditional sounding resources and mobile devices with excess soundingresources.

In a seventh possible implementation form of the computing apparatusaccording to the first aspect as such or to any of the preceding firstthrough sixth implementation forms of the first aspect the processor isconfigured to determine a first priority for the first deviceinformation based on the first device state and the first deviceinformation, determine a second priority for the second deviceinformation based on the second device state and the second deviceinformation, assign the first device information to a promotion listwhen a current sounding configuration of the first device informationcomprises fewer sounding resources than the first target soundingconfiguration, and assign the second device information to a demotionlist when the current sounding configuration of the second deviceinformation comprises more sounding resources than the second targetsounding configuration. This enables allocating sounding resources tomobile devices most likely to benefit from rich sounding.

In an eighth implementation form of the computing apparatus according tothe first aspect the processor is configured to determine the firstpriority for the first device based on at least one of a received signalstrength, a power headroom, and a location of a mobile device. Thisallows for rich sounding to be provided to mobile devices near the edgeof a cell.

In a ninth implementation form of the computing apparatus according tothe first aspect as such or to the seventh or eighth implementationforms of the first aspect the processor is configured to determine thefirst priority for the first device based on at least one of an amountof transmission resources, an uplink channel condition, and a quality ofservice of the mobile device. This can improve the allocation ofsounding resources.

In a tenth possible implementation form of the computing apparatusaccording to the first aspect as such or to the first through ninthimplementation forms of the first aspect, the processor is configured todetermine the first device priority or the second device priority basedon a weighted sum of features in the first device information or seconddevice information. This can improve the allocation of soundingresources.

In an eleventh possible implementation form of the computing apparatusaccording to the first aspect as such or to the seventh through tenthimplementation forms of the first aspect the processor is configured toremove the first device information from the promotion list when thefirst priority comprises a highest priority of the promotion list andoutput the first target sounding configuration. When there areinsufficient sounding resources available in a cell to support the firsttarget sounding configuration the processor is configured to remove thesecond device information from the demotion list when the secondpriority comprises a lowest priority of the demotion list, and outputthe second target sounding configuration. This can enable additionalsounding resources to be obtained.

In a twelfth possible implementation form of the computing apparatusaccording to the first aspect as such or to any of the preceding firstthrough eleventh implementation forms of the first aspect the processoris configured to initiate the determination of the target soundingconfiguration based on a timer. This can provide an improved triggeringof sounding resource configuration.

In a thirteenth possible implementation form of the computing apparatusaccording to the first aspect as such or to any of the previous firstthrough eleventh implementation forms of the first aspect the processoris configured to initiate the determination of the target soundingconfiguration based on an event, wherein the event comprises a mobiledevice disconnecting from a cell. This can provide an improvedtriggering of sounding resources.

According to a second aspect of the present disclosure the above andfurther objects and advantages are obtained by a method for allocatingsounding resources. In one embodiment the method includes determining afirst device state based on a device state model and a first deviceinformation, wherein the first device state model comprises a finitenumber of states. The method determines a first target soundingconfiguration for the first device information based on the first devicestate and outputs the first target sounding configuration. In thismanner, richer sounding configurations are provided without excessiveradio resource control reconfigurations.

In a first possible implementation form of the method according to thesecond aspect the method includes determining a second device statebased on the device state model and a second device information,determining a second target sounding configuration, wherein the secondtarget sounding configuration comprises fewer sounding resources than acurrent sounding configuration of the second device information. Whenavailable sounding resources for a cell are insufficient to support thefirst target sounding configuration, the method outputs the secondtarget sounding configuration to increase the available soundingresources in the cell. This provides for swapping of sounding resourcesbetween mobile devices requiring additional sounding resources andmobile devices with excess sounding resources.

In a second possible implementation form of the method according to thesecond aspect as such or to the first implementation form of the secondaspect the method includes determining a first priority for the firstdevice information based on the first device state and the first deviceinformation, and determining a second priority for the second deviceinformation based on the second device state and the second deviceinformation. The method assigns the first device information to apromotion list when a current sounding configuration of the first deviceinformation comprises fewer sounding resources than the first targetsounding configuration, and assigns the second device information to ademotion list when the current sounding configuration of the seconddevice information comprises more sounding resources than the secondtarget sounding configuration. This enables allocating soundingresources to mobile devices most likely to benefit from rich sounding.

In an third possible implementation form of the method according to thesecond aspect as such or to the first or second implementation forms ofthe second aspect the method includes removing the first deviceinformation from the promotion list when the first priority comprises ahighest priority of the promotion list and outputting the first targetsounding configuration. When there are insufficient sounding resourcesavailable in a cell to support the first target sounding configurationthe method includes removing the second device information from thedemotion list when the second priority comprises a lowest priority ofthe demotion list, and outputting the second target soundingconfiguration. This enables releasing sounding resources from lessactive mobile devices to make sounding resources available for use byhighly active mobile devices.

According to a third aspect of the present disclosure the above andfurther aspects and advantages are obtained by a computer programproduct comprising non-transitory computer program instructions thatwhen executed by a processing apparatus cause the processing apparatusto perform the method according to the second aspect.

These and other aspects, implementation forms, and advantages of theexemplary embodiments will become apparent from the embodimentsdescribed herein considered in conjunction with the accompanyingdrawings. It is to be understood, however, that the description anddrawings are designed solely for purposes of illustration and not as adefinition of the limits of the disclosed disclosure, for whichreference should be made to the appended claims. Additional aspects andadvantages of the disclosure will be set forth in the description thatfollows, and in part will be obvious from the description, or may belearned by practice of the disclosure. Moreover, the aspects andadvantages of the disclosure may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed out in theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the disclosure will be explained in more detail withreference to the example embodiments shown in the drawings, in which:

FIG. 1 illustrates a block diagram of an access node configured foradjusting the sounding resources allocated to mobile devices in a cellin accordance with the aspects of the disclosed embodiments.

FIG. 2 illustrates a flow chart of an exemplary method for allocation ofsounding resources in accordance with the aspects of the disclosedembodiments.

FIG. 3 illustrates an exemplary embodiment of a device state modelappropriate for determining buffer states in accordance with the aspectsof the disclosed embodiments.

FIG. 4 illustrates a graph showing the relationship between media accesscontrol layer throughput and device state in accordance with the aspectsof the disclosed embodiments.

FIG. 5 illustrates a block diagram of an exemplary embodiment of amethod for selecting a target sounding configuration in accordance withthe aspects of the disclosed embodiments.

FIG. 6 illustrates an exemplary embodiment of a method for calculatingpriority of a mobile device in accordance with the aspects of thedisclosed embodiments.

FIG. 7 illustrates an exemplary embodiment of a sounding resourceallocation algorithm incorporating aspects of the disclosed embodiments.

FIG. 8 illustrates an exemplary embodiment of a promotion list and ademotion list in accordance with aspects of the disclosed embodiments.

FIG. 9 illustrates a graph of the cumulative distribution function offile upload delay for an exemplary sounding resource allocationalgorithm incorporating aspects of the disclosed embodiments.

FIG. 10 illustrates an embodiment of a device state model having threebuffer states for a wireless communication system incorporating aspectsof the disclosed embodiments.

FIG. 11 illustrates exemplary promotion and demotion lists for awireless communication system incorporating aspects of the disclosedembodiments.

FIG. 12 illustrates an exemplary embodiment of a traffic statecalculator for a wireless communication system incorporating aspects ofthe disclosed embodiments.

FIG. 13 illustrates a state diagram for an exemplary embodiment of atraffic state model for a wireless communication system incorporatingaspects of the disclosed embodiments.

FIG. 14 illustrates a graph showing traffic state transitions and uplinkthroughput in a wireless communication system incorporating aspects ofthe disclosed embodiments.

FIG. 15 illustrates an exemplary embodiment of a resource block statemodel in a wireless communication system incorporating aspects of thedisclosed embodiments.

FIG. 16 illustrates exemplary data traffic patterns corresponding to aresource block state model in a wireless communication systemincorporating aspects of the disclosed embodiments.

FIG. 17 illustrates a block diagram of an exemplary computing deviceappropriate for implementing aspects of the disclosed embodiments.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

FIG. 1 illustrates a block diagram of an access node 100 configured toadjust the sounding resources allocated to one or more mobile devices150 in a cell. The term “cell” as used herein refers to an access node,all radio resource units controlled by the access node, and all mobiledevices whose radio transmissions and receptions are coordinated over acommon set of radio resources by the access node. The access node 100,which in certain embodiments may be an eNodeB 102, is the element in awireless communication system that is connected directly to mobiledevices 150 via a radio link or air interface. Among other functions,the access node 100 is responsible for configuring sounding referencesymbol reporting for each mobile device 150 to maximize uplinkperformance of the mobile devices 150. The uplink performance may bequantified using various metrics such as transmission delay, datathroughput, etc.

In certain embodiments the access node 100 may configure soundingreference symbol reporting or allocate sounding resources to improve theuplink performance of mobile devices 150 based on their location, suchas improving uplink performance of mobile devices located near the edgeof a cell. Much of the performance improvement achieved by allocation ofthe sounding resources is achieved through frequency selectivescheduling (FSS) made possible by frequency specific channelinformation.

Effective management of FSS requires an access node (AN) 100 or eNodeB102 to have frequency specific channel state information (CSI) for eachsub-band being scheduled. For scheduling downlink transmissions, theaccess node 100 can rely on a channel quality indicator (CQI) or otherdownlink channel condition information signaled by the mobile device 150over the physical uplink control channel (PUCCH) or the physical uplinkshared channel (PUSCH). Uplink channel conditions can be determined bythe access node 100 using sounding reference symbols (SRS) transmittedby the mobile device 150.

Channel quality estimation for the uplink scheduler is primarily basedon SRS transmitted by the mobile device 150. In certain instances uplinkestimation may also be based on the demodulation reference symbols(DM-RS) transmitted over the PUSCH. Sounding resources used for channelestimation may include SRS and/or DM-RS. For example, in each cell, oneor more single carrier frequency division multiple access (SC_FDMA)symbols or symbol positions are reserved for SRS transmission in everyradio frame, such as the 10 millisecond (ms) radio frame used in LTEbased cells. These reserved symbol positions, referred to herein assounding resources, are then shared among the mobile devices 150 usingvarious technologies such as time division multiple access (TDMA),interleaved frequency division multiple access (FDMA), and code divisionmultiple access (CDMA).

The access node 100 includes a radio resource control (RRC) unit 104that works with a radio link control (RLC) unit 106 to manage radioresources and manage connected mobile devices 150. An on-line device isa mobile device that is in an RRC connected state,transmitting/receiving data or expected to begin transmitting/receivingdata. The radio resource control unit 104 receives measurements from themobile devices 150 connected to the access node 100. These measurements108 include mobile device information, such as transmit buffer size,which is an indication of the amount of data in the mobile device 150waiting to be transmitted, device location, downlink channel stateinformation, SINR, etc. The mobile device measurements 108 may alsoinclude information about the applications running on the mobile device150, such as for example, VoIP, VoLTE, stock trading, streaming radio,and may also contain information about the data traffic type or qualityof service desired.

The access node 100 also includes a physical layer 120, which is thelowest layer in the communication stack made up of the physicalcommunication components. The physical layer 120 exchanges, i.e.,transmits and receives, data and other information with one or moremobile devices 150 within the cell or connected to the access node 100.Information passes between the physical layer 120 and the radio resourcecontrol 104 and radio link control 106 through the MAC layer 116.

A sounding resource manager 114 receives mobile device information 122associated with each mobile device 150 that is connected to the accessnode 100. Information about the status or state of each mobile device150 is maintained in a status unit 110 which in certain embodiments, aswill be described further below, may include various types of statemodels and sounding resource allocations and configurations. Thesounding resource manager 114 receives mobile device information 122from the radio resource control 104 and radio link control 106, andinformation such as device state 124 from the status unit 110. Thesounding resource manager 114 is configured to determine when thesounding configuration of a mobile device 150 needs to be changed. Whena configuration change is determined, the sounding resource manager 114requests 126 the radio resource control 104 to perform a radio resourcecontrol reconfiguration procedure to modify the sounding configurationof the mobile device 150. Sounding resources are managed on a per cellbasis so all sounding resources in a cell are managed by a singlesounding resource manager 114.

One particular exemplary sounding configuration, based on a 10 Megahertzcarrier frequency, could prescribe sounding over 12 RBs for each SRStransmission by a mobile device 150, requiring four transmissions tosound the entire frequency band. With this sounding configuration 48 RBsare used for sounding and 2 RBs are reserved for PUCCH and are thereforenot available for use by the PUSCH. A mobile device 150 that isconfigured with a 5 ms SRS periodicity could sound the whole frequencyband in 20 ms. This exemplary sounding configuration may be used in acell employing LTE type wireless communication standards where theuplink is configured such that each sub-frame includes one SC-FDMAsymbol for a sounding reference symbol.

Table 1 shows the exemplary sounding periods that may be configured forthe 10 sub-frames into which a single 10 ms LTE type radio frame may besplit. In the exemplary sounding configuration of Table 1, a mobiledevice 150 desiring rich sounding may be configured to transmit asounding reference symbol during two sub-frames of every 10 ms radioframe to provide a 5 ms sounding period. For the 5 ms sounding periodsub-frame 0 and sub-frame 5 are effectively paired to allow a mobiledevice 150 to transmit a sounding reference symbol every 5 ms.Similarly, sub-frame 1 is paired with sub-frame 6, and sub-frame 2 ispaired with sub-frame 7 for 5 ms sounding reference symboltransmissions.

TABLE 1 Subframe Number 0 1 2 3 4 5 6 7 8 9 SRS 5 ms 5 ms 5 ms 80 ms 80ms 5 ms 5 ms 5 ms 80 ms 80 ms period

Sub-frames 3, 4, 8 and 9 may be used to support mobile devices 150requiring a lower sounding rate. A mobile device 150 requiring fewersounding resources may be configured to have an 80 ms sounding period bytransmitting a sounding reference symbol once every eighth radio frame,in one of sub-frames 3, 4, 8 or 9.

When determining the number of users that may be supported by thesounding configuration shown in Table 1 some assumptions about the radiointerface are needed. Assuming a cyclic shift of 4, which equates to aCDMA factor equal to four, a comb factor of 2, and that each soundingtransmission covers resource blocks, there are four sounding referencesymbol transmissions to cover the entire sounding band of 48 resourceblocks. With these assumptions the sub-frame pair 0 and 5, and similarlysub-frame pairs 1-6 and 2-7, support 32 users with each sub-frame pair.

Table 2 shows the users supported by each sub-frame sounding referencesymbol transmission. Note, that since the same users that aretransmitting sounding reference symbols during sub-frames 0, 1 and 2also transmit sounding reference symbols during sub-frames 5, 6 and 7,the sub-frames 5, 6 and 7 do not support any additional users.

TABLE 2 Subframe Number 0 1 2 3 4 5 6 7 8 9 SRS 5 ms 5 ms 5 ms 80 ms 80ms 5 ms 5 ms 5 ms 80 ms 80 ms period Supported 32 32 32 256 256 256 256Users

In total, the exemplary sounding configuration described above supports96 mobile devices with 5 ms sounding and 1024 mobile devices with 80 mssounding. The sounding scheme using two sounding configurationsdescribed above is presented as an aide to understanding only and thoseskilled in the art will readily recognize that many other soundingperiod configurations are possible with different sounding periods andmore or less than two different sounding periods configured concurrentlyon different mobile devices in the same cell.

Since a limited number of mobile devices (96 in the above example) maybe configured for rich (5 ms sounding period in the above example)sounding, when a cell experiences a large volume of connected devices,not all connected devices may be configured for rich sounding. Aconventional method for allocating sounding resources is to use a firstcome first serve approach where a mobile device is configured for thebest available sounding period. With this approach the first 96 mobiledevices connecting to a cell would be configured for 5 ms soundingperiod and additional mobile devices would be configured to 80 mssounding as they connect to the cell. While easy to implement, thisapproach does not make efficient use of the sounding resources as thefirst mobile devices to connect may be near the center of the cell wheresignal strength is good and the throughput gain achieved with richsounding may not be large. It may also be the case that the devicesconfigured for rich sounding may not be transmitting data, in which casethe rich sounding resources are effectively wasted.

FIG. 2 illustrates a flow chart of an embodiment of a method 200 forallocating sounding resources appropriate for use in a sounding resourcemanager such as the sounding resource manager 114 described above andwith reference to FIG. 1. The method 200 begins by determining 202 adevice state or activity state of a mobile device 150 for which soundingresources are being allocated. The device state is based on deviceinformation and includes a variety of information about a particularmobile device 150 such as transmit buffer volume, traffic type of thecurrently running application on the mobile device 150, resource blockusage patterns, frequency of resource block allocations, or other mobiledevice and traffic characteristics.

The term “device information” as used herein refers to a set or othercollection of data and information pertaining to a single mobile device.The device information may include information collected by a mobiledevice 150 and sent to the access node 100, such as buffer volume, whichin an LTE like system may be sent with buffer status reports, downlinkchannel quality information such as the channel quality indicator (CQI),downlink signal to interference plus noise ratio (SINR), power headroomreports, information about the traffic type such as voice over internetprotocol (VoIP) or voice over long term evolution (VoLTE), and the typeof a running application, such as for example, a securities tradingapplication, web browsing application, or web posting application.

Device information may also include data and information determined atthe access node 100 based on signals received from the mobile device 150such as SINR of the uplink, number and frequency of resource blocksbeing granted to the mobile device 150 etc. Device information may referto the information about a mobile device 150 being serviced by theaccess node 100, or device information may refer to the mobile device150 itself where the meaning will become clear based on the context.

The device state is determined 202 using a state model for each mobiledevice 150 based on aspects of the activity of the mobile device 150 ingenerating user plane data for transmission over the uplink. The term“traffic” as used herein refers to the data being transmitted by themobile device 150 and refers to both the volume of data as well as otherdata transmission characteristics such as frequency of transmissions,etc. For example, in certain embodiments the device state characterizesthe status of the transmit buffer in the mobile device 150 and may bebased on buffer volume measurements. When this is the case the devicestate may be referred to as a buffer state.

A target sounding configuration is then determined 204 based on thedevice state determined in step 202 as well as other device information.In the exemplary sounding configuration described above, the targetsounding configuration is primarily the time period over which themobile device 150 sounds the entire carrier bandwidth. The soundingconfiguration determines the amount of sounding resources allocated to amobile device 150. Rich sounding provides a shorter sounding period andrequires a greater amount of sounding resources. The target soundingconfiguration of a mobile device 150 changes in accordance with changesto the mobile device condition, and these changes can occur many timesduring the active session of the mobile device 150.

In heavily loaded cells, all available sounding resources may be in use,which means all radio resources allocated for sounding reference symboltransmission are being used by a mobile device 150 connected to thecell. When this occurs additional sounding resources may not beallocated to a newly connected mobile device or to a mobile deviceneeding additional sounding resources until sounding resources have beenreclaimed from a mobile device disconnecting from the cell or bychanging the sounding configuration of a connected mobile device to alower sounding configuration. A lower sounding configuration is onerequiring fewer sounding resources.

Essentially there is competition among mobile devices 150 for availablesounding resources. To determine which mobile devices should get theirtarget sounding configuration and which mobile devices should receivelower sounding configurations, a priority is calculated 206 for eachmobile device 150. The calculated priority 206 may be based on thedevice state as well as the device information. Sounding resources arethen allocated based on the target sounding configuration and priorityof each mobile device 150.

One embodiment of a device state is based on transmit buffer volumes ofa mobile device 150 and may be referred to as a buffer state. Forexample, in certain wireless systems, the transmit buffer volume isavailable at an access node 100 through buffer status reports (BSR)which are sent by mobile devices 150 over the uplink. FIG. 3 illustratesan embodiment of a finite state machine 300 having two buffer statesappropriate for determining a buffer state for a mobile device such asmobile device 150. In the finite state machine 300, a first buffer state302 represents a mobile device 150 having a low buffer volume and asecond buffer state 304 represents a mobile device 150 having a highbuffer volume. When a mobile device 150 becomes radio resource controlconnected it is initialized to the low buffer state 302. Thereafter,while the mobile device 150 remains radio resource control connected,the device state is updated according to the finite state machine 300.Transitions between the low buffer state 302 and the high buffer state304 occur based on thresholds and timers.

When the buffer volume of a mobile device 150 exceeds a first threshold,such as 6000 bits, for a first predetermined period of time, such aszero or more milliseconds, the device state moves or transitions 306 tothe high buffer state 304. When the buffer volume of a mobile device 150falls below a second predetermined threshold, such as 100 bits, for asecond predetermined period of time, such as 25 ms, the device statemoves or transitions 308 to the low buffer state 302. The thresholds andtime periods may be configured by an operator, hard coded in the accessnode 100, or automatically updated from time to time based oninformation about the cell.

Using a low value for the buffer volume thresholds allows users withlower transmission volumes to benefit from rich sounding and possiblyobtain better performance. However, low buffer volume thresholds resultin a greater number of radio resource control reconfigurations to adjustthe sounding resources and sounding reference symbol transmissionperiods, especially when the cell loading is high. With higher buffervolume thresholds, fewer radio resource reconfigurations occur, andmobile devices sending large data volumes, such as large file uploadsand attachments, should benefit. Therefore, selection of the buffervolume thresholds, influences overall behavior and performance of thewireless network.

FIG. 4 illustrates a graph 400 showing the relationship between mediaaccess control (MAC) layer throughput and device state for the finitestate machine or device state model 300 having two buffer states. MACthroughput is shown in the upper graph 402 where the vertical axis 406represents MAC layer throughput in bits per second and the horizontalaxis 410 shows time in seconds. The lower graph 404 shows buffer stateof a mobile device 150 where a value of 1 on the vertical axis 408represents the low buffer state 302 and a value of 2 on the verticalaxis 408 represents the high buffer state 304. The values of one and twoare derived, as will be discussed in further detail below, from valuesassigned to the buffer states during priority calculations.

In the example of FIG. 4, at about five (5) seconds 412 the mobiledevice 150 places a large amount of data into its transmit buffercausing the buffer state 404 to transition to the high buffer state 304.From about five seconds 412 until about six and a half seconds 414 themobile device 150 transmits the data as shown by the MAC throughput 416during this period.

Once the data transmission has completed and the transmit buffer volumeof the mobile device 150 falls below the predetermined threshold valuefor a predetermined period of time the buffer state 404 transitions atabout six and a half seconds 414 back to the low buffer state 302. Eachtime 418, 420 the mobile device 150 transmits a large volume of data,the buffer state transitions to the high buffer state and the MACthroughput increases until the data transmission has completed.

A target sounding configuration for a mobile device 150 is determinedbased on the device state of the mobile device 150 and may also be basedon other values in the device information. In certain embodiments thedevice state may be a buffer state such as the buffer state derived fromthe device state model 300 described above. Alternatively, other typesof device states based on different criteria and different device statemodels may be used for determination of a target sounding configurationfor the mobile device 150. Determining a target sounding configurationbased on a device state derived from a device state model provides moreefficient use or allocation of sounding resources than conventionalapproaches.

In conventional approaches it is common to assign a soundingconfiguration on a best available basis, where a mobile device 150 isgiven the best available configuration when it connects to an accessnode 100 resulting in all the rich sounding configurations beingassigned to the first mobile devices to connect and subsequent mobiledevices receiving a lower sounding configuration when they connect. Thisoften results in rich sounding configurations being assigned to mobiledevices that are doing little or no data transmission and low soundingconfigurations being assigned to devices doing large data uploads. A lowsounding configuration is a sounding configuration that has few or a lowamount of sounding resources providing a longer sounding period and lessaccurate channel information. To meet quality of service requirements itmay be necessary to perform a radio resource control reconfiguration tochange the sounding configuration each time a mobile device 150 beginsto transmit data.

Radio resource control reconfigurations incur overhead, using radioresources that could otherwise be used for data transmissions and alsorisk connection loss and dropped phone calls. An alternative strategydisclosed herein is to assign only a justifiable amount of soundingresources to a mobile device 150 when it connects where the amount ofsounding resources assigned are based on determination of a targetsounding configuration.

In one embodiment the target sounding configuration may be based on thebuffer state as described above. Mobile devices 150 with a higher volumebuffer state 304 will have a better target sounding configuration thanmobile devices 150 with a lower volume buffer state 302. This is donebecause mobile devices 150 in the high buffer state 304 will betransmitting more data than mobile devices 150 in the low buffer state302, and will likely benefit more from having a rich soundingconfiguration. Mobile devices 150 in the low buffer state 302 will alsobenefit indirectly from this sounding resource assignment. Fewerresource blocks will be used up by mobile devices 150 in the high bufferstate 304 due to the better throughput achieved from use of richsounding. Basing sounding configuration on device state means thatsounding configurations may be changed each time mobile devices 150connect or change their device state with minimal overhead or cost.

An embodiment of determining a target sounding configuration for amobile device 150 based on buffer state may be based on the two bufferstates 302, 304 in the device state model 300 described above. In asystem having two sounding configurations referred to as X and Y, wheresounding configuration X has a sounding period of 5 ms and soundingconfiguration Y has a sounding period of 80 ms, the two buffer states302, 304 can be directly mapped to the two sounding configurations X andY as shown in Table 3. While in the low buffer state 302, correspondingto a mobile device 150 having a low transmit buffer volume, the mobiledevice 150 does not need rich sounding and can be allocated a loweramount of sounding resources such as the 80 ms sounding period providedby sounding configuration Y. When the mobile device 150 moves into thehigh buffer state 304 where the mobile device 150 has a large volume ofdata in its transmit buffer, the mobile device 150 is likely to benefitfrom a large number of sounding resources and shorter sounding period, 5ms, corresponding to the richer sounding configuration X. The richsounding provided by sounding configuration X allows for betterfrequency selective scheduling to improve uplink transmissions for themobile device 150.

With the use of device states, such as the buffer states 302, 304, whenan active mobile device 150 is in the low buffer state 302, the mobiledevice 150 will be assigned a lower amount of sounding resourcescorresponding to sounding configuration Y even though there are enoughsounding resources available to assign the mobile device 150 to the highsounding configuration X. By assigning sounding resources based on thedevice state, when a mobile device 150 transitions to a higher bufferstate 304 it is easier to assign a richer sounding configuration Xwithout having to downgrade a mobile device in the lower buffer state302 from sounding configuration X to sounding configuration Y.

TABLE 3 Preferred Sounding sounding Buffer State configuration period[ms] 304 X 5 302 Y 80

FIG. 5 illustrates a block diagram of an exemplary embodiment of amethod 500 for selecting a target sounding configuration 510 based ontransmit buffer volume or size 506. In the block diagram illustrated inFIG. 5, and similarly in subsequent figures, the boxes 502, 504represent processing elements and the arrows 506,508,510 represent dataitems passed into or created by the processing elements 502, 504. Theexemplary method 500 receives transmit buffer volume 506 from a mobiledevice 150 and uses the transmit buffer volume 506 to calculate 502 ordetermine a buffer state 508 for the mobile device 150. Determination ofthe buffer state 508 may be based for example on the two buffer statemodel 300 described above in which case the buffer state 508 would beone of the two buffer states 302 or 304. The determined buffer state 508is then used to determine 504 a preferred sounding configuration 510.Determination 504 of the target sounding configuration 510 is based onthe buffer state 508, which in the present example is a buffer statesuch as buffer state 302 or buffer state 304, and may be determinedusing a mapping, such as the mapping described above and shown in Table3. Alternatively other determination 514 means may be used includingmappings and computations based on device information corresponding tothe mobile device 150 being configured.

To aide selection of which mobile devices should be reconfigured, apriority is calculated for each mobile device and is used to determinethe relative importance that different mobile devices should receive fortheir target sounding configuration. Priority for a given mobile device150 is based on the device information for that mobile device and on thedevice state determined 502 for the mobile device.

For example, in the exemplary embodiment described above, priority maybe calculated based on two inputs. The first input is the buffer statefrom the buffer state model 300. The low buffer state 302 is assigned avalue, for the purposes of priority calculation, of one and the highbuffer state 304 is assigned a value of two. The second input to theexemplary priority calculator is the downlink (DL) reference symbolreceived power (RSRP). The downlink reference symbol receive power hasunits of decibel-milliwatts (dBm) and may be used in the prioritycalculation without further modifications. The downlink reference symbolreceive power is representative of the downlink path loss andapproximates the uplink path loss of a mobile device 150. The uplinkpath loss helps identify the distance between the mobile device 150 andthe serving access node 100.

Mobile devices 150 near the edge of the cell are farther away from theserving access node 100 and will likely experience a greater path lossthan a mobile device 150 that is close to the serving access node 100.The mobile devices 150 on the cell edge tend to have the lowest uplinkthroughput since full path loss compensation is not used in uplink powercontrol due to power limitations in mobile devices. Mobile devices 150can thus be differentiated based on their buffer state 302 or 304, andtheir path losses. An exemplary embodiment of a priority calculation isshown in Equation 1:

P _(md) =KB _(s) −RSRP _(dl),  (1)

where P_(md) is the priority being calculated for the mobile device,B_(s) is the buffer state value as described above, and RSRP_(dl) is thedownlink reference symbol receive power of the mobile device, and K is aconstant. The constant K can in general take on any desired values. Incertain embodiments it is beneficial to keep the value of the constant Kroughly greater than the possible range of values for the downlinkreference symbol receive power, RSRP_(dl) of the mobile device.

For example in the exemplary priority calculation shown in Equation (1)the constant K may be about 500. The transmit buffer volume of themobile device may be used in the priority calculation after beingquantified as a buffer state as described above, or alternatively theuplink transmit buffer volume of the mobile device 150 may be used inthe priority calculation unchanged with units such as bits.

FIG. 6 illustrates an exemplary embodiment of a method 600 forcalculating priority of a mobile device 150. Calculation of the mobiledevice priority may be combined with the mobile device target soundingconfiguration determination method 500 described above and withreference to FIG. 5. The mobile device priority calculator 602 takes asinput the mobile device buffer state 508 along with the reference symbolreceive power in dBm 604. The priority calculator assigns a value toeach buffer state 508, such a value of one (1) for the low buffer state302 and a value of two (2) for the high buffer state when using a twobuffer state model 300 as described above. A priority calculation 602such as the priority calculation shown in Equation (1) is performed toproduce a priority 606 for the mobile device 150.

A sounding resource allocation algorithm for a cell can now beconstructed using the target sounding configuration determination andpriority calculation described above and with reference to FIG. 6. Anexemplary embodiment of a sounding resource allocation algorithm 700 isillustrated in FIG. 7. The exemplary sounding resource allocationalgorithm 700 may be used to allocate sounding resources to activemobile devices 150 within a cell. Sounding resources are the radioresources used for sounding reference symbol transmission. The soundingresource allocation algorithm 700 compares the target soundingconfiguration determined based on the device state of a mobile device150 to the current sounding configuration of the mobile device 150. Whenthe current sounding configuration is worse or includes fewer soundingresources than the target sounding configuration determined for themobile device 150, the sounding resource allocation algorithm 700attempts to promote or upgrade the mobile device 150 to its targetsounding configuration.

When all sounding resources in a cell are in use or there are not enoughsounding resources available to promote the mobile device 150, theavailable sounding resources may be increased by demoting a mobiledevice whose current sounding configuration includes more soundingresources than required by the target sounding configuration for thatmobile device, thereby freeing up additional sounding resources that maythen be used to promote another mobile device. Under heavily loaded cellconditions, this process of demoting one device to free up soundingresources for another device often results in swapping soundingconfigurations or sounding resources between a mobile device that is notcurrently transmitting data and a mobile device that is beginning a datatransmission.

The sounding resource allocation algorithm 700 is scheduled to runrepeatedly and may be configured to run periodically or a periodicallybased on a timer such as every 100 ms or other desired time interval.Alternatively the sounding resource algorithm 700 may be triggered by achange to the sounding resources being used in a cell. This can occurwhen a mobile device 150 leaves the cell, a new mobile device connectsto the cell, or when there is a change to the target soundingconfiguration of a mobile device, such as when the device state of amobile device changes. Each pass of the allocation algorithm 700 begins702 based on the desired trigger.

A target sounding configuration to be used during the next time periodis determined 704 for each mobile device 150 connected to the accessnode 100. The term “next time period” refers to a period of time that issubsequent to or occurs after the current pass of the resourceallocation algorithm 700 has completed and mobile devices have beenreconfigured based on the sounding configuration outputs 708, 716 by thesounding resource allocation algorithm 700.

Determination 704 of the preferred or target sounding configuration foreach mobile device 150 being serviced by the access node 100 may be doneby, referring to FIG. 2, determining 202 a device state based on adevice information and a device state model, then determining 204 apreferred or target sounding configuration based on the device state.The mobile devices are then placed onto a promotion list or a demotionlist 706 based on the current sounding configuration and target soundingconfiguration of each mobile device 150.

When a determined target sounding configuration for a mobile device 150requires more sounding resources than it currently has, the mobiledevice 150 is placed on the promotion list. When a determined targetsounding configuration for a mobile device 150 requires fewer soundingresources than it currently has, the mobile device 150 is placed on ademotion list. When there are multiple devices on the promotion anddemotion lists it may become difficult to determine which mobile devicesshould be promoted and which mobile devices should be demoted. To aid inthe selection of a mobile device for promotion and demotion a priorityis calculated 708 for each mobile device on both the promotion list andthe demotion list and each list is sorted based on the calculatedpriorities.

The mobile devices on the promotion and demotion lists are thenprocessed by a reconfiguration process 720. The reconfiguration process720 attempts to promote the mobile devices for which the respectivesounding configuration requires more sounding resources than it iscurrently using. When there are insufficient sounding resourcesavailable in the cell to promote all mobile devices on the promotionlist, the reconfiguration process 720 demotes mobile devices on thedemotion list in order to increase the available sounding resources forpromotion of mobile devices.

In one embodiment, the reconfiguration process checks 710 the promotionlist 734 for a mobile device requiring additional sounding resources. Ifthere are no mobile devices 150 on the promotion list 724, branch 722 istaken and the reconfiguration process 720 is complete and proceeds toexit 718. When there is a mobile device 150 on the promotion list, step710 removes the highest priority mobile device from the promotion list734 and proceeds on branch 724 where a check is made 712 to determine ifthere are enough available sounding resources to upgrade the mobiledevice removed from the promotion list 734 at step 710 to its targetsounding configuration. When sounding resources are available branch 728is taken and the target sounding configuration is output to the mobiledevice 150 and the reconfiguration process 720 returns to step 710 tocheck the promotion list 734 for another mobile device to be removed andpromoted.

If at step 712 it is determined that there are insufficient soundingresources available to promote the mobile device that was removed fromthe promotion list 734 at step 710, the reconfiguration process 720proceeds along branch 712 where at step 714 the demotion list 736 ischecked and a mobile device is removed from the demotion list 736. Whenthere are no mobile devices on the demotion list 736, branch 732 istaken and the reconfiguration process 720 is complete and proceeds tothe exit 718. When there is a mobile device on the demotion list 736,branch 730 is taken and the mobile device is removed from the demotionlist and its sounding configuration is downgraded at step 716, byoutputting the target sounding configuration for the removed device,thereby freeing up sounding resources that may be used to upgrade amobile device desiring additional sounding resources.

The reconfiguration process 720 then returns to step 712 where a checkis made to determine if there are sufficient available soundingresources to upgrade the mobile device that was removed from thepromotion list 736 at step 710. The reconfiguration process 720continues iterating through the promotion list until there are no mobiledevices remaining on the promotion list, or until all devices on thedemotion list have been downgraded and all sounding resources in thecell are in use. The promotion list contains all mobile devices thathave a target sounding configuration requiring more sounding referencesymbol resources than their current sounding configuration, while thedemotion list contains all mobile devices that have a target soundingconfiguration requiring fewer sounding reference symbol resources thantheir current sounding configuration.

With the finite state machine 300 having two buffer states 302, 304described above, each mobile device 150 can be assigned to one of onlytwo states: a low buffer state 302, and a high buffer state 304. Table 4shows how mobile devices may be assigned to the promotion and demotionlists based on their current buffer state and the current and targetsounding configurations. The first three columns list the possiblebuffer state, current sounding configuration, and target soundingconfiguration, while the last column shows the list assignment for eachrespective combination of buffer state and sounding configurations.

In the embodiment shown in Table 4 the system has two possible soundingconfigurations referred to as X and Y, where sounding configuration Xhas a sounding period of 5 ms corresponding to a sounding configurationrequiring more sound reference symbol resources than soundingconfiguration Y, and sounding configuration Y has a sounding period of80 ms corresponding to a sounding configuration requiring fewer soundingreference symbol resources than sounding configuration X. As can be seenin Table 4 when a current sounding configuration for a mobile device 150is the same as the target sounding configuration for the mobile device150, the mobile device 150 is not placed on either the promotion list orthe demotion list.

TABLE 4 Device's Device's Device's current target Action taken bufferstate configuration configuration toward Device 304 X X No action taken304 Y X placed on promotion list 302 X Y placed on demotion list 302 Y YNo action taken

FIG. 8 illustrates an exemplary embodiment of a promotion list 802 anddemotion list 816 as may be formed from the two buffer state model andtwo sounding configuration example shown in Table 4. Once mobile deviceshave been placed on the respective promotion and demotion lists, apriority is calculated, such as with the priority formula in Equation(1) above, for each mobile device on each list. The lists are sortedaccording to the calculated priority of each mobile device 150. Thepromotion list 802 is sorted with increasing priority as shown by thearrow 812 resulting with the highest priority mobile device being placedat the top 808 of the promotion list 802 and the lowest priority mobiledevice placed at the bottom 810 of the promotion list 802.

In the sounding resource allocation algorithm 700 mobile devices areremoved and processed from the top of each list so the first mobiledevice to be promoted will have the highest priority and the firstmobile device demoted will have the lowest priority. Because in theexemplary embodiment illustrated in FIG. 8, the priority calculation isbased on the reference symbol receive power for each mobile device,mobile devices with lower reference symbol receive power are placed atthe top 808 of the promotion list. Since the distance between a mobiledevice 150 and the access node 100 is inversely correlated with thereference symbol receive power, this prioritization results in mobiledevices located near the cell center being placed toward the bottom ofthe promotion list 806 and mobile devices located farther from theaccess node 100 being located toward the top 804 of the promotion list.The reconfiguration algorithm 720 considers devices for promotion inorder from highest priority 808 to lowest priority 810 on the promotionlist. Thus, with the priority calculation based on reference symbolreceived power as shown in Equation 1, preference is given to cell edgedevices thereby providing better performance to the cell edge devices.

In a heavily loaded cell, where all or nearly all the sounding referencesymbol resources are in use, it becomes necessary to downgrade a mobiledevice which currently has a high resource sounding configuration inorder to free up sounding resources for promotion of another mobiledevice. Two mobile devices essentially swap or exchange their soundingconfigurations or sounding resources.

To determine which mobile device 150 should be demoted to free upsounding resources, a demotion list 816 is used. The demotion list 816is similar to the promotion list 802 except it is sorted in reverseorder 826 with the highest priority mobile device being placed at thebottom 824 of the demotion list 816 and the lowest priority mobiledevice being placed at the top 822. With the previous prioritycalculation example shown in Equation 1, sorting 826 places mobiledevices near the cell center toward the top 818 of the demotion list andmobile devices near the cell edge toward the bottom 820 of the demotionlist 816. The lowest priority mobile device 822 is taken from thedemotion list 816 to have its sounding configuration swapped orexchanged with the highest priority device 808 taken from the promotionlist.

FIG. 9 illustrates a graph 900 of the cumulative distribution function(CDF) of file upload delay for the exemplary embodiment of the soundingresource allocation algorithm 700 described above having two bufferstates and two sounding configurations, as compared to a baseline systemusing a first come first serve approach to sounding resource allocation.The cell illustrated by the graph 900 is based on a simulated wirelessnetwork that includes 170 mobile devices performing a file transferprotocol data upload and 50 mobile devices engaged in instant messaging.In the graph 900, the horizontal axis 906 represents file upload delayin seconds, and the vertical axis 908 represents a cumulativedistribution function (CDF) with a value between zero and 1.

The first graph 912 illustrated with a broken line provides the CDF fora baseline system, and the second graph 910 illustrated with a solidline shows the CDF for a system incorporating the exemplary finite statemachine 300 based sounding resource allocation algorithm 700. Thegreatest performance improvements, nearly 10%, are achieved in the area904 around 1 second of delay. An enlargement of this portion 904 of thegraph 900 is provided by the inset graph 902. As can be seen in thegraphs 900 and 902, the improved sounding resource allocation algorithm700 described herein provides significantly improved performance over abaseline system.

In certain embodiments it is advantageous to use device state modelshaving more than two states in order to better characterize the mobiledevice data traffic and improve selection of the target soundingconfiguration. FIG. 10 illustrates a exemplary embodiment of a devicestate model 1000 having three buffer states, B1, B2, and B3. The threebuffer states B1, B2, and B3 may be used to represent three transmitbuffer volume levels where buffer state B1 represents a low buffervolume, buffer state B2 represents a medium buffer volume, and bufferstate B3 represents large buffer volumes. The advantage of the threebuffer state model 1000 over the two buffer state model is that thethree buffer state model 1000 allows prioritization of mobile deviceshaving large buffer volumes over those mobile devices with only mediumbuffer volumes. Preference for a rich sounding configuration is given bythis device state model 1000 to mobile devices that will need to bescheduled more frequently over a longer period of time to empty theirtransmit buffers. The sounding resource allocation algorithm 700 remainsunchanged except that determination of the target configurations 704 andcalculation of priorities 708 is based on a three buffer state model1000.

State transitions for the three buffer state model 1000 are determinedby two threshold volumes thB2 and thB3. In one embodiment the low buffervolume threshold thB2 may be about 1000 bits and the high buffer volumethreshold may be about 6000 bits. A delay time T may also be used toavoid chattering or unwanted transitions between states. Table 5 showsthe state transitions for the three buffer state model 1000. The firstcolumn, initial buffer state, shows the starting state for eachtransition and the second column, final buffer state, shows the endingstate for each transition. The last column, condition for transition,shows the conditions causing the transition between the buffer states.In the last column, “volume” is the transmit buffer volume of the mobiledevice.

In the embodiment shown in Table 5 transitions from a higher bufferstate to a lower buffer state 1004, 1006, 1012 occur after the transmitbuffer volume falls below a threshold volume, thB2 or thB3, for acertain period of time T. Transitions from a lower buffer volume stateto a higher buffer volume state 1008, 1002, 1010 occur when the transmitbuffer volume exceeds a threshold volume thB2, thB3.

In certain embodiments is desirable to use a timer value for all statetransitions 1002, 1004, 1006, 1008, 1010, 1012. A first timer value maybe used for transitions 1002, 1008, 1010 from a lower buffer state to ahigher buffer state. A second timer value may be used for transitions1004, 1006, 1012 from a higher buffer state to a lower buffer state.

TABLE 5 Initial Final Buffer Buffer state state Condition for transitionB1 B2 thB3 >= Volume > thB2 (1008) B1 B3 Volume > thB3 (1010) B2 B3Volume > thB3 (1002) B2 B1 Volume < thB2 for period T (1006) B3 B2Volume < thB3 for period T (1004) B3 B1 Volume < thB2 for period T(1012)

The target sounding configuration may be determined from the threebuffer state model 1000 using a mapping or other algorithm. Oneembodiment of a mapping from buffer state to target soundingconfiguration is illustrated in Table 6. Table 6 shows a mapping fromthe buffer state B1, B2, B3 depicted in the buffer state model 1000, tothe two sounding configurations X and Y described above. Alternatively asystem having more or less than two sounding configurations may beadvantageously employed with buffer state model 1000 and the soundingresource allocation algorithms disclosed herein. Both buffer states B2and B3 receive the same target sounding configuration. However, as willbe discussed further below, buffer states B2 and B3 receive differentpriority values.

TABLE 6 Target Sounding sounding Buffer State configuration period [ms]B3 X 5 B2 X 5 B1 Y 80

Calculation of priority values for the three buffer state model 1000 maybe done using the priority formula shown earlier in Equation (1).However, the three buffer states are assigned different values for thepurposes of priority calculation: buffer state B1 has a value of 1, B2has a value of 2, and B3 has a value of 3. With these values for eachbuffer state B1, B2, B3, mobile devices having a buffer state of B3receive higher priority, and consequently preference for promotion, overmobile devices having a buffer state of B2.

The promotion and demotion lists are generated and sorted 708 asdescribed above. Mobile devices with a target sounding configurationrequiring more sounding resources than their current soundingconfiguration are placed on the promotion list and mobile devices havinga target sounding configuration requiring fewer sounding resources thantheir current configuration are placed on a demotion list. FIG. 11illustrates an embodiment of a promotion list 1102 and a demotion list1104 resulting from a sounding resource allocation algorithm 700 basedon the three buffer state model 1000 referred to above. Sorting thepromotion list 1102 and demotion list 1104 based on the prioritizationequation, Equation (1), results in an advantageous structure of thelists 1102, 1104.

The promotion list 1102 is sorted based on the calculated priority asshown by the arrow 1114. As before, the mobile device with the highestpriority 1106 is removed for promotion first and the mobile device withthe lowest priority 1122 is promoted last. Mobile devices with thelargest buffer volumes corresponding to buffer state B3 are at the top1142 of the promotion list and receive preference for promotion overmobile devices with medium buffer volumes corresponding to buffer stateB2 which are located near the bottom 1144 of the promotion list 1102.

Using the reference symbol receive power in the priority calculation,equation (1), mobile devices for promotion are ordered such that mobiledevices having large buffer volumes located near the edge of the cell1110 are promoted first. Mobile devices with large buffer volumes nearthe cell center 1112 are promoted next followed by promoting mobiledevices with medium buffer volumes near the edge of the cell 1118.Mobile devices with medium buffer volumes near the cell center arepromoted last.

The demotion list 1104 is sorted as indicated by the arrow 1124 with thelowest priority mobile devices scheduled to be demoted first at the top1126 of the demotion list 1104 and the highest priority devices at thebottom 1140 of the demotion list 1104. All mobile devices on thedemotion list 1104 are in the low buffer volume state B1 however, incertain embodiments it may be advantageous to structure the demotionlist 1104 with mobile devices that were previously in the medium bufferstate B2 towards the top 1146 of the demotion list 1104 and mobiledevices that were previously in the high buffer state B3 toward thebottom 1148 of the demotion list 1104. Including information about theprevious device state of a mobile device may be accomplished by using adifferent priority calculation formula for mobile devices on thedemotion list 1104 where the priority calculation used for the demotionlist takes a mobile device's previous device state into account.

In certain embodiments it is advantageous to include information aboutthe type of data traffic expected as well as transmit buffer volume. Forexample, a device state model may include knowledge of the name ofapplications running on the mobile device, or the quality of serviceclass indicator (CQI), as well as scheduled data volumes. A device statemodel including information about the traffic type is referred to hereinas a traffic state model, or a traffic state.

A block diagram of an exemplary traffic state calculator 1202 isillustrated by the block diagram 1200 in FIG. 12. Using a traffic statecalculator 1202 with knowledge of data traffic type can supplement thebuffer volume knowledge to more accurately predict which mobile deviceswill benefit most from rich sounding. This is especially true for voicetraffic. In the buffer state models described above, the target soundingconfiguration was determined based on information collected during aprevious time period, while the determined target sounding configurationwill be used by the mobile device during a next time period. It istherefore desirable to enhance the device state model and ultimately thedetermination of the target sounding configuration with calculationsthat better predict the conditions that will be present during a nexttime period.

In the traffic state model 1200 a traffic state calculator is configuredto determine a traffic state 1212 based on a number of inputs includingthe transmit buffer volume of the mobile device 1204, scheduled datavolumes for the mobile device 1206, a quality of service class indicator(QCI) 1208, and traffic type 1210. The traffic type may includeknowledge of the running application such as voice communication,instant messaging, web posting, stock trading, etc.

An exemplary embodiment of a traffic state model 1300 is illustrated inFIG. 13 where the exemplary traffic state model includes five trafficstates. It should be understood that the five traffic state model ispresented only as an aide to understanding and that device state modelswith more or less than 5 states may be advantageously employed in asounding resource allocation algorithm 700 without straying from thespirit and scope of the disclosed embodiments. In this example, thetraffic states T1, T2, T3, T4, T5, are numbered from one to five wheretraffic state T1 is assigned to mobile devices having the lightest datatraffic and traffic state T5 is assigned to mobile devices having theheaviest data traffic.

Traffic state T1 represents a traffic condition where only occasional,small data packets, are being transmitted by the mobile device, such asdata packets that may be handled by one resource block. Traffic state T2represents a traffic condition where larger occasional data packets,such as data packets requiring several resource blocks, are beingtransmitted by the mobile device. Traffic state T3 represents a trafficcondition where a mobile device is frequently transmitting smallpackets, such as during a talk spurt in VoIP. Traffic state T4represents a traffic condition with bursts of large amounts of data,such as data bursts requiring more than about 20 ms to clear the buffer.Traffic state T5 represents a traffic condition with a very large volumeof data, such as when the transmit buffer is nearly full. The trafficstate model 1300 allows state transitions between any of the fivetraffic states T1, T2, T3, T4, T5 to any other of the traffic states T1,T2, T3, T4, T5 as indicated by the bi-directional arrows, one of whichis indicated by numeral 1302.

A mobile device may be placed in traffic state T1 when it is idle orvery inactive. An idle or inactive mobile device may be recognized forexample through buffer volume measurements received from the mobiledevice. If it is known that the mobile device is running a voiceapplication, such as VoIP or VoLTE, then when a talk spurt on the uplinkis identified the mobile device may be moved to traffic state T3. Thetransition from traffic state T1 to traffic state T3 is an example of atraffic state transition that is determined based on both buffer volumeand knowledge of the application or traffic type of the mobile device.Traffic state T2 may be determined by measuring the interval betweenpacket bursts, which can be determined by measuring the times duringwhich the transmit buffer is empty, and comparing this interval to anidle threshold such as about 100 ms.

When the idle interval exceeds the idle threshold and the volume perdata packet burst is less than a predetermined threshold for maximumpacket burst volume, the mobile device may be placed in traffic stateT2. Traffic state T4 may be determined similar to traffic state T2 witha larger threshold for the packet burst volume, such as about 50kilobytes. When it is recognized that the transmit buffer is nearly fullor the transmit buffer is occupied for most of a predeterminedassessment period, such as about one second, the mobile device may beplaced in traffic state T5.

Once the traffic state of a mobile device has been determined a targetsounding configuration may be determined for the mobile device based onthe traffic state.

TABLE 7 Target Sounding Sounding configuration Traffic StateConfiguration update period T5 C  5 T4 B 10 T3 A 80 T2 A 80 T1 XInfinite (no sounding)

Table 7 illustrates an exemplary embodiment of a mapping from the fivetraffic state model 1300 described above to target soundingconfigurations as may be advantageously employed in a wirelesscommunication system using four sounding configurations. The richestsounding configuration, C, has a sounding period of 5 ms, the nextrichest sounding configuration, B, has a sounding period of 10 ms, andthe lowest sounding configuration, C, has a sounding period of 80 ms. Itis also possible in the wireless communication system illustrated byTable 7 to have some mobile devices with no sounding resources where thesounding configuration using no sounding resourced is denoted as X.

In Table 7, the first column lists the five possible traffic states, T1,T2, T3, T4, T5, the second column lists the corresponding soundingconfigurations, A, B, C, X, and the third column shows the soundingperiod for each sounding configuration. Using the mapping shown in Table7, the target sounding configuration for a mobile device can bedetermined directly from the device state.

For the purposes of priority calculation, the values of 1 through 5 maybe assigned to the traffic states T1 through T5 respectively. A priorityformula, such as the priority formula shown in Equation (1), may then beused to determine a priority for each mobile device. It should be notedthat basing priority on the downlink reference symbol received power isonly one possible way of prioritizing devices. Alternatively, thepriority calculation could be based on the distance between a mobiledevice 150 and the serving access node 100 giving priority to mobiledevices 150 that are closer or farther from the serving access node 100,or on a quality of service for which a mobile device has contracted. Asnoted above, in certain embodiments it is desirable to use differentpriority formula for the promotion list and the demotion list.

FIG. 14 illustrates a graph 1400 showing traffic state transitions 1408and uplink throughput 1406 for a mobile device that is uploading largefiles via a protocol such as file transfer protocol (FTP). Thehorizontal axis 1416 represents time in seconds. The vertical axis 1402of the upper graph 1406 represents uplink throughput in bits per secondand the vertical axis 1404 of the lower graph 1408 shows the trafficstate T1 and T4. The graph 1400 shows how when the uplink throughputincreases, such as the point indicated by numeral 1414, the trafficstate transitions at the time indicated by numeral 1410 to traffic stateT4 and remains in traffic state T4 until the upload completes around thetime indicated by numeral 1412.

A second large uplink transmission occurs around the time indicated bynumeral 1418 and as can be seen by the state transition graph 1408 thetraffic state transitions between traffic state T1 and traffic state T4until the upload completes. As discussed above, when the traffic statetransitions to traffic state T4, the target sounding configurationincludes rich sounding to improve uplink throughput performance duringthe file upload. When the upload completes, the traffic statetransitions back to the idle traffic state T1 allowing the mobile deviceto be demoted to a lower sounding configuration.

In certain embodiments it is advantageous to base the device state modelon resource blocks (RB) used by a mobile device. A state model based onresource block usage, referred to herein as an RB-state model, can bebased on both the number of resource blocks granted to a mobile device150 by the access node 100 and how frequently resource blocks aregranted. A resource block state of this type can be calculated using thefrequency of scheduling events, i.e. the frequency with which an accessnode 100 grants resource blocks to a mobile device 150, and the numberof resource blocks consumed or used by the mobile device 150 during eachscheduling event. The RB-state is configured to represent a mobiledevice need for resource blocks. The resource block state model is moreadvanced that either the buffer state or traffic state models describedabove. Rich sounding should be given to mobile devices that can benefitmost from the additional sounding resources. A mobile device using alarge number of resource blocks may lose the benefits provided byfrequency selective scheduling since the bandwidth allocated to themobile device may exceed the coherence bandwidth of the channelresulting in a frequency diverse allocation. A mobile device using avery small number of resource blocks is only sending small packets ofdata so the potential benefit provided by rich sounding are small.

State transitions in the RB-state model may be based on current and pastmeasurements, i.e. measurement history, of the frequency of schedulingevents and the number of resource blocks consumed using for examplestatistical traffic classification. The RB-state model assumes channelconditions are relatively stable going forward so that a target soundingconfiguration determined based on current and past measurements will bevalid during the next time period. Alternatively, in certain embodimentsit is beneficial to use a predictive algorithm based not only on thefrequency and number of resource blocks as described above but alsoincluding additional information such as mobile device transmit buffervolume, cell load, modulation and coding scheme, mobile device powerheadroom, or other values with benefit to the prediction algorithm.

Knowledge of the applications running in the mobile device can alsoimprove device state predictions. For example application knowledge isof significant value in the case of a VoIP application. A predictivestate transition algorithm could identify trends in the measurementhistory and use this to make a more accurate prediction of the state ofthe mobile device during the next time period.

When determining RB-state transitions using a measurement basedapproach, device state may be determined using simple logic such asdescribed above for the traffic state model 1300. FIG. 15 illustrates anexemplary embodiment of a five RB-state model 1500 that may be used tocharacterize the state or condition of a mobile device. The exemplaryRB-state model 1500 includes five RB-states R1, R2, R3, R4, R5. Allstate transitions are supported as shown by the transition arrows, whereone of the transition arrows is indicated by numeral 1502. In RB-stateR1 the mobile device is idle or very nearly idle. An idle mobile devicemay be determined based on past measurements of resource block usagewhere a device in RB-state R1 has very infrequent resource blockallocations and each resource block allocation is very small such asless than two resource blocks.

When a mobile device is running a VoIP or VoLTE bearer and a talk spurtis identified on the uplink the mobile device is moved to RB-state R3.In this case a combination of resource block quantity and knowledge ofthe application type is used to determine the RB-state. When knowledgeof the executing application is not available, transitions into RB-stateR3 may be based on other criteria such as a frequent but low volumescheduling of resource blocks. A RB-state of R3 may be identified ashaving a mean resource block usage being small or below a predeterminedthreshold RT1 such as about 4. The variance of resource block usage mayalso be small or below a predetermined threshold RT2 such as about 16,and mean time between new transmissions, i.e. not countingre-transmissions, is small or below a predetermined threshold RT3 suchas about 20 ms. RB-state R4 may be determined in a similar fashion tothe determination of RB state R3 with different thresholds such as RT1about 20 and RT2 about 100. Note the exemplary threshold values givenfor RT1, RT2, and RT3 are appropriate for a carrier bandwidth of about10 megahertz (MHz) or about 50 resource blocks. In different wirelesscommunication systems, different threshold values may be advantageouslyemployed.

The RB-state R2 may be determined by measuring the interval betweenpacket bursts, i.e. by measuring the times when the transmit buffer isempty. The measured time interval can then be compared to apredetermined threshold value such as about 100 ms. When the intervalexceeds the threshold and the mean resource block allocation per packetburst is lower than a first predetermined threshold, such as about 20but greater than a second threshold such as about 5, the mobile devicewould be in RB-state R2. A mobile device would be in RB-state R5 when itreceives frequent scheduling of resource blocks, such as about every 20ms, and the mean resource block consumption for each scheduling event islarge such as above about 20.

FIG. 16 illustrates exemplary data traffic patterns corresponding toeach of the RB-states in the RB-state model 1500 described above. Thehorizontal axis 1612 in each graph 1600, 1602, 1604, 1606, representstime, and the vertical axis 1610 in each graph 1600, 1602, 1604, 1606represents a number of resource blocks granted to a mobile device by theservicing access node. Each vertical bar, such as the vertical barindicated by numeral 1608 represents a scheduling event, which is thetime when resource blocks are granted to a mobile device. The height ofeach bar 1608 represents the number of resource blocks granted to themobile device during the scheduling event.

RB-state R2 is characterized by larger occasional transmissionsrequiring several resource blocks each as depicted in the graph 1600.RB-state R3 is characterized by frequent relatively small transmissionssuch as the traffic generated by an uplink talk spurt in VoIPcommunications as depicted in graph 1602. RB-State R4 is characterizedby frequent transmissions requiring a medium volume of resource blockseach as depicted in graph 1604. RB-State R5 is characterized by frequentlarge transmissions as depicted by the graph 1606. RB-State R1 ischaracterized by little or no uplink data transmissions and is notdepicted in FIG. 16.

Determination of an appropriate target sounding configuration for eachRB-state in the RB-State model 1500 may be achieved using any of thepriority formula described herein, such as the mapping from five devicestates to four sounding configurations shown in Table 7. Determinationof target sounding configuration for each device state should strive togive a richer target sounding configuration to mobile devices that havegreater throughput requirements or to mobile devices that will benefitmost from richer channel sounding.

Determination of priority values for each mobile device when using aresource block state model may be based on a priority formula similar tothe priority formula shown in Equation (1) above. For purposes ofpriority calculation, integer values may be assigned to each RB-Statewith RB-states requiring higher throughput receiving a greater value aswas described above with respect to the traffic state model 1300.Alternatively, real values other than integers may be assigned to devicestate allowing certain device states to be favored more than others byassigning higher weights to device state that should be promoted first.

In certain embodiments it is desirable to consider multiple featureswhen distinguishing which mobile devices should be promoted or demotedfirst within a cell. It may also be desirable, as described above withreference to the three buffer state model 1000, to employ differentpriority formula for the promotion list and the demotion list. Forexample, a priority formula could include several features such as powerheadroom as may be obtained from power headroom reports in a LTE typesystem, resource block allocation statistics collected by an access nodewhile allocating resource blocks to each mobile device, quality ofservice, as well as other mobile device information.

These features may be incorporated into a priority formula using aweighted sum as shown in Equation (2):

P _(md)=Σ_(i)(w _(i)feature_(i)),  (2)

where feature_(i) represents a feature being considered and w_(i) is aweighting factor used for feature_(i). The feature_(i) may include forexample an average variance or other resource block statistic, transmitbuffer size of the mobile device, power headroom etc. For certainfeatures it is sometimes desirable to apply normalization or filteringto the feature value prior to priority computation with Equation (2).The weighting factors w_(i) may all be configured equal (such as addingup to one) or they may be configured to give greater weight orimportance to some features. The weighting for a particular feature maybe based on variance of the feature value. For example if a particularfeature has a larger variance than another feature being considered inthe priority formula, Equation (2), the feature with a larger variancemay be given a smaller weight to compensate for the greater variance. Incertain embodiments all the features may be normalized in which caseapplying weights may not be required.

FIG. 17 illustrates a block diagram of an exemplary computing device1700 appropriate for implementing aspects of the disclosed embodiments.The illustrated computing device 1700 includes a processor 1702 coupledto a computer memory 1704, a network interface 1706, and a userinterface (UI) 1708. The computing apparatus 1700 is appropriate for useas a computing device, which in certain embodiments may be a node in awireless communications system, and is appropriate for implementing anyof the methods, such as the exemplary sounding resource allocationalgorithm 700 described herein.

The processor 1702 may be a single processing device or may comprise aplurality of processing devices including special purpose devices, suchas for example, digital signal processing (DSP) devices,microprocessors, specialized processing devices or general purposecomputer processors. The processor 1702 may be configured to implementany of the methods for allocating sounding resources described herein.In certain embodiments the processor may include a CPU working in tandemwith a graphics processing unit (GPU) and may include a DSP to handlesignal processing tasks. The processor 1702 may also include one or moreprocessing cores configured for parallel processing.

The processor 1702 is coupled 1712 to a memory 1704 which may be acombination of various types of volatile and non-volatile computermemory such as for example read only memory (ROM), random access memory(RAM), magnetic or optical disk, or other types of computer accessiblememory. The memory 1704 stores computer program instructions that may beaccessed and executed by the processor 1702 to cause the processor toperform a variety of desirable computer implemented processes or methodssuch as allocation of sounding resources in a wireless network.

The program instructions stored in memory 1704 may be organized as setsor groups of program instructions referred to in the industry withvarious terms such as programs, software components, software modules,units, etc. Each module may include a set of functionality designed tosupport a certain purpose. For example a software module may be of arecognized type such as an operating system, an application, a devicedriver, or other conventionally recognized type of software component.Also included in the memory 1704 are program data and data files whichmay be stored and processed by the processor 1702 while executing a setof computer program instructions.

In certain embodiments the computing device 1700 includes a networkinterface 1706 coupled to the processor 1702 and configured tocommunicate with other processing entities in a wireless communicationnetwork. The network interface 1706 may be of a standardized type, suchas Ethernet, or may be specific to a particular network implementation.In certain embodiments the network interface 1706 may include a radiofrequency unit capable of communicating over a wireless communicationnetwork.

The UI 1708 may include one or more user interface elements such as atouch screen, keypad, buttons, voice command processor, as well as otherelements adapted for exchanging information with a user. The UI 1708 mayalso include a display unit 1710 configured to display a variety ofinformation appropriate for a computing device or mobile user equipmentand may be implemented using any appropriate display type such as forexample organic light emitting diodes (OLED), liquid crystal display(LCD), as well as less complex elements such as LEDs or indicator lamps.In certain embodiments the display unit 1710 incorporates a touch screenfor receiving information from the user of the computing device 1700.Alternatively, the computing apparatus may not include a UI 1708 and maybe configured to be controlled and administered remotely through thenetwork interface 1706.

Thus, while there have been shown, described and pointed out,fundamental novel features of the disclosure as applied to the exemplaryembodiments thereof, it will be understood that various omissions,substitutions and changes in the form and details of devices and methodsillustrated, and in their operation, may be made by those skilled in theart without departing from the spirit and scope of the disclosure.Further, it is expressly intended that all combinations of thoseelements, which perform substantially the same function in substantiallythe same way to achieve the same results, are within the scope of thedisclosure. Moreover, it should be recognized that structures and/orelements shown and/or described in connection with any disclosed form orembodiment of the disclosure may be incorporated in any other disclosedor described or suggested form or embodiment as a general matter ofdesign choice. It is the intention, therefore, to be limited only asindicated by the scope of the claims appended hereto.

What is claimed is:
 1. A computing apparatus for use in an access node,the computing apparatus comprising: a processor; and a non-transitorycomputer-readable storage medium coupled to the processor and storingprogramming instructions which, when executed by the processor, instructthe processor to: determine a first device state based on a device statemodel and first device information, wherein the device state modelcomprises a finite number of states, determine a first target soundingconfiguration for the first device information based on the first devicestate, and output the first target sounding configuration.
 2. Thecomputing apparatus of claim 1 wherein the programming instructions,when executed by the processor, further instruct the processor to:determine the first device state based on an amount of data in atransmit buffer.
 3. The computing apparatus of claim 2 wherein theprogramming instructions, when execute by the processor, furtherinstruct the processor to: move the first device state to a higherbuffer state when the amount of data in the transmit buffer exceeds afirst predetermined threshold for a first predetermined period of time;and move the first device state to a lower buffer state when the amountof data in the transmit buffer drops below a second predeterminedthreshold for a second predetermined period of time.
 4. The computingapparatus of claim 1 wherein the programming instructions, when executedby the processor, further instruct the processor to: determine the firstdevice state based on an amount of data in the transmit buffer, anamount of data transmitted, and a traffic type.
 5. The computingapparatus of claim 1 wherein the programming instructions, when executedby the processor, further instruct the processor to: determine the firstdevice state based on a current and past quantity of resource blocks inthe first device information and/or a current and past frequency of datatransmissions in the first device information.
 6. The computingapparatus of claim 5 wherein the programming instructions, when executedby the processor, further instruct the processor to: estimate a deviceinformation value for a next time period based on one or more pastdevice information values; and determine the resource block state basedon the estimated device information value.
 7. The computing apparatus ofclaim 1 wherein the programming instructions, when executed by theprocessor, further instruct the processor to: determine a second devicestate based on the device state model and a second device information;determine a second target sounding configuration, wherein the secondtarget sounding configuration comprises fewer sounding resources than acurrent sounding configuration of the second device information; andwhen available sounding resources for a cell are insufficient to supportthe first target sounding configuration, output the second targetsounding configuration to increase the available sounding resources inthe cell.
 8. The computing apparatus of claim 1 wherein the programminginstructions, when executed by the processor, further instruct theprocessor to: determine a first priority for the first deviceinformation based on the first device state and the first deviceinformation; determine a second priority for the second deviceinformation based on the second device state and the second deviceinformation; assign the first device information to a promotion listwhen a current sounding configuration of the first device informationcomprises fewer sounding resources than the first target soundingconfiguration; and assign the second device information to a demotionlist when the current sounding configuration of the second deviceinformation comprises more sounding resources than the second targetsounding configuration.
 9. The computing apparatus of claim 8 whereinthe programming instructions, when executed by the processor, furtherinstruct the processor to: determine the first priority for the firstdevice based on at least one of a received signal strength, a powerheadroom, and a location of a mobile device.
 10. The computing apparatusof claim 8 wherein the programming instructions, when executed by theprocessor, further instruct the processor to: determine the firstpriority of the first device based on at least one of an amount oftransmission resources, an uplink channel condition, and a quality ofservice of the mobile device.
 11. The computing apparatus of claim 8wherein the programming instructions, when executed by the processor,further instruct the processor to: remove the first device informationfrom the promotion list when the first priority comprises a highestpriority of the promotion list; output the first target soundingconfiguration; and when there are insufficient sounding resourcesavailable in a cell to support the first target sounding configuration:remove the second device information from the demotion list when thesecond priority comprises a lowest priority of the demotion list, andoutput the second target sounding configuration.
 12. The computingapparatus of claim 1 wherein the programming instructions, when executedby the processor, further instruct the processor to: initiate thedetermination of the target sounding configuration based on a timer. 13.The computing apparatus of claim 1 wherein the programming instructions,when executed by the processor, further instruct the processor to:initiate the determination of the target sounding configuration based onan event, wherein the event comprises a mobile device disconnecting froma cell.
 14. A method for allocating sounding resources, the methodcomprising: determining a first device state based on a device statemodel and first device information, wherein the first device state modelcomprises a finite number of states; determining a first target soundingconfiguration for the first device information based on the first devicestate; and outputting the first target sounding configuration.
 15. Themethod of claim 14, further comprising: determining, the first devicestate based on an amount of data in a transmit buffer.
 16. The method ofclaim 14, further comprising: determining the first device state basedon an amount of data in the transmit buffer, an amount of datatransmitted, and a traffic type.
 17. the method of claim 14, furthercomprising: determining the first device state based on a current andpast quantity of resource blocks in the first device information and/ora current and past frequency of data transmissions in the first deviceinformation.
 18. The method of claim 17, further comprising: estimatinga device information value for a next time period based on one or morepast device information values; and determining the resource block statebased on the estimated device information value.
 19. The method of claim14, further comprising: determining a second device state based on thedevice state model and a second device information; determining a secondtarget sounding configuration, wherein the second target soundingconfiguration comprises fewer sounding resources than a current soundingconfiguration of the second device information; and when availablesounding resources for a cell are insufficient to support the firsttarget sounding configuration, outputting the second target soundingconfiguration to increase the available sounding resources in the cell.20. A computer program product comprising non-transitory computerprogram instructions that when executed by a processing apparatus causethe processing apparatus to: determine a first device state based on adevice state model and first device information, wherein the firstdevice state model comprises a finite number of states; determine afirst target sounding configuration for the first device informationbased on the first device state; and output the first target soundingconfiguration.